1. Field of the Invention
The present invention relates to a clutch apparatus for a washing machine, and more particularly, to a clutch apparatus for a washing machine for controlling rotary power transmitted from a driving motor to a basket shaft using electromagnetic force.
2. Description of the Background Art
FIG. 1 is a vertical sectional view for a washing machine with a clutch apparatus according to a conventional technology.
In general, a washing machine, as shown in FIG. 1, includes a case 111 for forming a housing space inside, a tub 113 installed in the case 111, the tub 113 for storing water inside, a spin basket 115 rotatably positioned in the tub 113, the spin basket 115 for washing laundry, a pulsator 119 positioned in the spin basket 115 to be in a relative rotary motion with respect to the spin basket 115, the pulsator 119 for forming a water current, and a driving motor 125 formed in the lower portion of the tub 113, the driving motor 125 for providing driving power to the spin basket 115 and the pulsator 119.
FIG. 2 is a vertical sectional view showing the clutch apparatus according to the conventional technology, which is included in the above washing machine.
A basket shaft 117 formed of a hollow member on the bottom of the spin basket 115 is combined with the spin basket 115. The basket shaft 117 is rotatably supported to the tub 113 and a bearing housing 130 by bearings 114.
A pulsator shaft 121 that rotates while being directly coupled with the driving motor 125 so as to rotate the pulsator 119 is inserted into the basket shaft 117. The pulsator shaft 121 is supported to the basket shaft 117 by bearings 120 so as to be in the relative rotary motion.
The driving motor 125 includes a stator 129 fixed to the lower portion of the bearing housing 130 fixed to the tub 113 and a rotor 127 connected from the outer circumference of the stator 129 to the center of the stator 129 and combined with the pulsator shaft 121.
In particular, a clutch device 131 is included between the bearing housing 130 and the rotor 127 so as to selectively transmit the rotary power generated by the driving motor 125 to the basket shaft 117.
The clutch device 131 includes a solenoid actuator 137 fixed to the lower portion of the bearing housing 130, the solenoid actuator 137 for generating electromagnetic force, a coupling member 133 combined with around the basket shaft 117, the coupling member 133 for transmitting or intercepting the rotary power while being in an up and down motion due to the electromagnetic force of the solenoid actuator 137, thus being combined with or being separated from a serration member 122 fixed to the rotor 127, a spring member 141 installed between the coupling member 133 and the bearing housing 130, the spring member 141 for providing elasticity to the coupling member 133 so that the coupling member 133 moves due to the electromagnetic force and then, is returned to an original position.
The solenoid actuator 137 includes a solenoid coil 138 positioned on the outer circumference of the coupling member 133, the solenoid coil 138 for forming an electric field, and a solenoid case 139 fixed to the bearing housing 130, the solenoid case 139 for supporting the solenoid coil 138.
The coupling member 133 includes a serration coupling 134a combined with around the basket shaft 117 by a serration method, the serration coupling 134a combined with or separated from the serration member 122 and a magnetic coupling 134b integrally fixed to around the serration coupling 134, the magnetic coupling 134b for generating force corresponding to the solenoid coil 138.
That is, a shaft tooth 118 and a rotor tooth 123 are respectively formed on the outer circumference of the basket shaft 117 and the outer circumference of the serration member 122. A coupling tooth 135 is formed on the inner circumference of the serration coupling 134a. The coupling tooth 135 transmits the rotary power of the driving motor 125 to the basket shaft 117 or intercepts the rotary power of the driving motor 125 from the basket shaft 117 while being in the up and down motion along the shaft tooth 118, thus combined with or separated from the rotor tooth 123.
The operation of the washing machine with the clutch apparatus according to the conventional technology will now be described.
When the laundry is washed or is dried after finishing washing the laundry while integrally rotating the spin basket 115 and the pulsator 119, the laundry is washed/dried by driving the driving motor 125 in a state where power is not supplied to the solenoid actuator 137, that is, the solenoid actuator 137 is turned off.
At this time, the coupling tooth 135 simultaneously gears with and is combined with the shaft tooth 118 and the rotor tooth 123 in a state where the coupling member 133 moves downward due to the elasticity of the spring member 141. Therefore, the spin basket 115 integrally rotates together with the pulsator 119.
When the laundry is washed while rotating only the pulsator 119 in a state where the spin basket 115 is stopped, the power is applied to the solenoid actuator 137. The electromagnetic force generated by the solenoid coil 138 forms a magnetic path for connecting the magnetic coupling 134b of the coupling member 133, the central region of the rotor 127, and the basket shaft 117 to each other via the bearing housing 130 positioned in the upper portion of the solenoid case 139 and the solenoid case 139. At this time, the magnetic force operates as attraction in the direction, where magnetic reactance is minimized, that is, the direction, where the magnetic coupling 134b of the coupling member 133 approaches to the bottom of the solenoid case 139.
Accordingly, the coupling tooth 135 of the coupling member 133 is separated from the rotor tooth 123 and is combined with only the shaft tooth 118, the rotary power transmitted from the driving motor 125 is not transmitted to the spin basket 115 and is transmitted to only the pulsator 119.
When the power supplied to the solenoid actuator 137 is intercepted in such a state, the coupling member 133 falls due to the elasticity of the spring member 141 and self-weight. Accordingly, the coupling tooth 135 simultaneously gears with the shaft tooth 118 and the rotor tooth 123.
However, in the clutch apparatus of the washing machine according to the conventional technology, since the solenoid actuator 137 is formed to use direct current (DC) power, an additional DC power supply circuit for supplying the DC must be included. Also, flux leaks since many parts that can be magnetized are arranged around the solenoid actuator 137. In particular, since the thickness of the bearing housing 130 and the thickness of the solenoid case 139 are about 2 mm, respectively, thus the degree of self-saturation is high, the leakage of the flux deteriorates.
Also, the magnetic force becomes larger than motive power for raising the coupling member 133 at an initial stage as the coupling member 133 rises, thus the distance between the coupling member and the solenoid coil becomes narrower. Accordingly, when the coupling member 133 rises, excessive magnetic force is generated. Also, when the coupling member 133 rises and reaches the final position, the magnetic force becomes stronger. Accordingly, the coupling member 133 collides with the bearing housing 130, thus causing collision noise.
When the elasticity of the spring member 141 increases so as to rapidly fall the coupling member 133 against the magnetic force caused by residual flux, a holding voltage applied to the solenoid coil 138 must be increased in order to maintain the state where the coupling member 133 rises. Accordingly, consumption of power increases.